A series of 4260 consecutive echocardiographic examinations, performed in 5 Cardiological Centers was examined, identifying 125 intraventricular false tendons (FTs) in 100 cases (55 normals and 45 with heart disease) of whom 31 were female and 69 male, aged 3 to 82 years. An anatomo-morphological study was possible in 9 cases, dead for stroke or heart failure, on autopsy, and in 7, on heart surgery. A phonocardiogram was performed in all normals and in 20 patients. On echocardiography, FTs appeared as an echo-producing string-like structure, straight between the septum and the ventricular free wall, mobile during the cardiac cycle, without systolic thickening and any relation with the atrioventricular valvular apparatus. The prevalence of FTs was 2.3%; it was 3.2% to 5.3% in younger people. FTs were located in the right ventricle (4 cases), left ventricle (95 cases) or in both (1 case). Their site was left apical (45 FTs), right apical (2 FTs), right (3 FTs) and left (20 FTs), upper septum-to-free wall (55 cases). In 1 case hypertrophy of trabeculae of the left ventricle was detected. FTs were single (79 cases), double (19 cases), multiple (2 cases), short (42 cases), long (58 cases), thick (45 cases) and thin (55 cases). They showed a membrane-like motion (thick FTs-45 cases) and a valve-like motion (thin FTs-55 cases). Innocent murmur was detected in 50 of 55 normals and related to thin FTs. Of 16 cases examined anatomically and histologically, FTs were fibrous in their distal portion and fibro-muscular in the proximal one in 12 cases, whereas they were entirely fibrous-muscular in 4 cases. The site and location of FTs detected by echo were confirmed by anatomy in all cases. In 4 cases other 9 FTs, not detected on echocardiography, were found. These data suggest that echocardiography is a useful tool to detect intraventricular FTs and differentiate them from other echo-producing structures. Although a relationship between FTs and heart disease has not been found, their presence could be responsible of innocent murmur in many normal subjects.